The present invention relates to a cutting tool and particularly to an adjustable rotary drill.
When drilling or boring relatively large diameter holes, it has been found that standard twist drills do not readily provide accurate round holes and are very difficult to employ with light duty drilling apparatus such as hand electric drills or small drill presses.
In order to accurately drill relatively large holes, therefore, a twist drill is typically used only to form a relatively small diameter pilot hole which is subsequently enlarged by a cutting tool. There are available several types of cutting tools having adjustable cutting elements for enlarging pilot holes to the desired size. Representative of such prior art are U.S. Pat. Nos. 2,937,545, issued May 24, 1960, to P. A. Rauer, et al; 3,358,531, issued Dec. 19, 1967, to W. Schaffler; 2,811,054, issued Oct. 29, 1957, to L. L. Townsend; and 3,318,175, issued May 9, 1967, to S. A. Cogsdill. These prior art cutting tools either provide specialized cutting elements which are relatively large and thereby suffer to some extent the same problems as a conventional twist drill or involve relatively complex structure for the mounting of the adjustable cutting elements to the shank of the drill. Further, these cutting tools are not suitable for use in pilot holes which may be out-of-round and/or undersized.